1. Field of the Invention
The present invention relates to a cooker which uses induction heating to heat a pot for cooking by sauteing or other means.
2. Description of the Prior Art
Progress in technology which uses induction heating to heat magnetic pots has led to the recent development of rotary cookers which use induction heating to heat rotary pots for automatic sauteing. An electromagnetic cooker disclosed in the Japanese Patent Application Laid-Open No. 63-175375 is such an example, and FIG. 33 shows a partial cross-section of the side of the cooker.
In FIG. 33, receptacle 2 is mounted on top of main unit 1, which has a built-in heating power supply, by hinge 3 so that it can rotate freely, and supported and fixed by support member 4 at a desired inclination angle. Support member 4 consists of first support lever 4b and second support lever 4c which are joined together by pin 4a, and supports and fixes receptacle 2 at a desired angle by tightening pin 4a. Pot 7 is located at the central part of receptacle 2 in such a way that it can be rotated on axis 9 by driving unit 8 at the bottom. Induction heating coil 6 is wired around pot 7 via heat insulator 5. Lid 10 is screwed onto the top of receptacle 2 and slip ring 11 is provided between lid 10 and pot 7 to prevent ingredients inside pot 7 from escaping from receptacle 2. In addition, there is small lid 12 on the central top of the lid for inserting seasonings. Numbers 13 and 14 are control units for rotation speed and heating temperature or time, respectively, and 15 is ingredients.
As an example to saute ingredients, using the cooker described above, incline receptacle 2 at a desired angle by support member 4 and turn on induction heating coil 6 to heat the outside of pot 7 while actuating driving unit 8 to rotate pot 7. Then, put oil into pot 7 and stop the rotation when oil spreads all over pot 7. Put ingredients 15 to be sauteed into the pot, cover with lid 10 and rotate pot 7. Then, ingredients 15 are heated, stirred and sauteed within pot 7. At a proper time, open small lid 12 to add seasonings and cooking is over.
The conventional electromagnetic cooker is configured and used as described above.
(a) However, since receptacle 2 of the above electromagnetic cooker is inclined manually, it is not easy to use. There is a risk of users' getting burnt especially when changing the inclination angle of the receptacle during operation, .
(b) The pot for holding ingredients is heated by induction heating coil 6. However, heating coil 6 consists of only one layer, thus providing-only a single cooking pattern. Therefore, the cooker can do only sauteing, and is thus limited in its application range.
(c) The types of cooking possible with this cooker is limited.
(d) In addition, its heating method is very simple, cooking methods and heating times are limited, resulting in a narrow application range.
(e) As the rotation speed of the pot is fixed and does not change during cooking, it has been difficult to enhance the sauteing performance.
(f) Induction heating coil 6 is wired between the side and the bottom of cooking pot 7 via heat insulator 5 to heat ingredients 15 inside the pot from the outside. Therefore, when cooking pot 7 is inclined, the top of cooking pot 7 where there are no ingredients is also heated, resulting in a waste of electricity as well as a large size, complex structure and high production cost for induction heating coil 6.
(g) Furthermore, since cooking pot 7 is rotated at a fixed speed and heated uniformly, ingredients 15 do not contact all parts of cooking pot 7, thus take a long time to cook. In addition, induction heating coil 6 is wired between the side and the bottom of cooking pot 7 via heat insulator 5 to heat ingredients 15 from the outside. Therefore, when cooking pot 7 is inclined, the top of cooking pot where there are no ingredients 15 is heated, resulting in a waste of electricity, and a large size, complex structure and high production cost for induction heating coil 6.
(h) Cooking pot 7 fixed on the tip of rotary axis 9 is rotated by actuating driving unit 8. Flange 7a of cooking pot 7 is rotated while in contact with slip ring 11 fixed on stationary lid 10 to seal up the pot. Therefore, too tight a sealing results in increased friction, the wearing of contact surfaces, and the generation of a gap which hinders the rotation of cooking pot 7. On the other hand, too loose a sealing results in soup running out from the gap to the inside of receptacle 2. Since cooking pot 7 is fixed, it is difficult to clean after cooking and, accordingly, it becomes easily dirty.
(i) When ingredients are to be sauteed, for instance, users must feel the temperature of the pot from the ambient temperature by putting their hands into cooking pot 7. Therefore, there is a risk of their getting burnt when they put their hands into the pot. Since the temperature of the cooking pot is unknown during cooking, heating temperature is controlled by the perception and experience of users. As a result, they cannot go away from the rotary cooker during cooking. If they go away from the cooker, the temperature of the cooking pot goes too high, resulting in scorching and an eventual danger of fire. In addition, when the cooking pot is heated continuously without ingredients inside, it becomes too hot and damages the receptacle.
(j) Cooking using the electromagnetic cooker is carried out as described above. Since the cooking temperature is unknown, the timing for adding oil and seasonings and the timing for taking out sauteed food rely on the perception and experience of cooks. In addition, if cooks go away from the cooker during cooking, ingredients are scorched and there is a danger of fire.